Previous research suggests that it is profitable to try to describe the operations performed by visual neurons in terms of a generalized transform of the visual image, and that a decomposition of their visual response properties into component sinusoidal gratings is a particularly apt transform to use. A quantitative study of the properties of single units in the lateral geniculate nucleus and in areas 17 and 18 of the visual cortex will be undertaken to produce such a decomposition of their receptive fields, to analyze the neural mechanisms that lead to particular features of this decomposition, and to relate the results obtained to those of classical studies using geometric stimuli. Unit activity will be recorded from adult cats using conventional techniques, and the visual stimuli generated and unit responses analyzed with a laboratory digital computer, which will make possible a superior experimental paradigm designed to reduce or eliminate the problems due to fluctuations in sensitivity seen in units in these structures. Electrical stimulation of the afferents and efferents of the units will be performed in order to produce a neuronal model of the receptive field mechanisms of single cells, and this model will then be used in an attempt to explain certain properties of the human visual system, particularly its processing of pattern and movement information. This research will significantly increase our knowledge of the electrophysiological correlates of central visual processing